sapei ± 500 kvdc - 1000 mw interconnection sardinia ... borgo sabotino sapei 24-01-14.pdf ·...

SAPEI± 500 kVdc - 1000 MW interconnection

Sardinia – Italian peninsula

HVDC links in Italy

SA.CO.I.Monopolar connection (triterminal)200 kV dc – 300 MW(Sardinia-Corsica-continental Italy)

SA.PE.I. (work in progress)Bipolar connection 500 kV dc – 1000 MW (Sardinia – Italian peninsula)(Sardinia – Italian peninsula)

ITALY- GREECE Monopolar connection 400 kV dc – 500 MW

(Italy-Greece)

Preliminary considerations

� To increase the security, the reliability and the quality of supply of

load in Sardinia

� To reduce the cost of reserve and guarantee a better utilization of

generation at peak load condition

� To promote the export of energy generated in Sardinia

SAPEI Feasibility study

� To guarantee the reduction of constrains to sardinian operators for

the participation to the electricity market

Long life span of SACOI

(submarine cable in service in 1967)

MAIN HYPOTHESES TO EVALUATE THE RATING OF THE HVDC LINK

Generation capacity and demand in SardiniaHydro plants:

� few plants with little capacity, one pumping plant with a great capacity (Taloro

200 MW)

� no new plants foreseen


Thermal plants

� 4 great carbon plants (tot. 1800 MW), of which more than half has the priority

Demand: 2000 MW in the first year with an yearly growth rate of 2,7%

Wind plants:

� a great number of plants planned

�Foreseen 700 MW in the first year, 900 MW in 2010 and 1200 MW in 2015

� 4 great carbon plants (tot. 1800 MW), of which more than half has the priority

of dispatch

� no new plants foreseen in the first year, 1 combined cycle of 400 MW in 2010

and 1 combined cycle of 400 MW in 2015

Definition of scenarios

Hypotheses:

� It is assumed that the generation in the continent is more expensive than in Sardinia, given the presence of carbon and wind plants.

� SACOI is supposed to be not in service


Main hypotheses to evaluate the rating of the HVDC link

� SACOI is supposed to be not in service

� Corsica is supplied by a AC link of 50 MW

� Time frame reference: year commissioning (2007), 2010, 2015

RESULTS

The results of the feasibility study has pointed out that:

� the link is substantially used to export power from Sardinia to continent

� the power that flows across the link substantially grows in the years, following

the increase of generation capacity in Sardinia

Studies of the power flow across the link and the costs foreseen gives:


Studies of the power flow across the link and the costs foreseen gives:

� the optimal rating of the link is 500 kVdc / 1000 MW;

� to optimize the flow across the link is given by the opportunity tocontract the link in two phases; with the SACOI in service during thefirst phase of SAPEI, the growth of capacity between Sardinia andthe continent to 700 MW, allows the maximization of the productionin Sardinia

Converter terminals : FIUME SANTO (Sardinia) – LATINA (Italian peninsula)

Power cable ±500 kVdc

• Length of submarine cable : 2x 420 km

• Maximum depth: 1620 m

SAPEI - main technical data

• Length of land cable : 2x1km (Sardinia) + 2x14 km (Latium)

Employment of existing upgrated anode SACOI linked to terminal with

submarine cable (32 km) and land cable (1 km)

New cathode at Latina linked to terminal with submarine cables (2x8 km)

and land cables (2x14 km)

Converter station

Fiume Santo substation

<0.5 km <1 km

Sea land joint 420 km

Latina substation and converter

station

14 km

Maximum depth 1640 m

SAPEI – Physical scheme

Sea land joint

Submarine cables

Tyrrenian sea

SARDINIA LATIUM

AC cables Dc cables Dc cables

** in air substation* GIS substation

*

Municipality involved: Sassari, Porto Torres, Castelsardo (anode punta Tramontana)

Municipality involved: Nettuno (Rm), Latina

**

SAPEI – single line diagram

SAPEI – Main aspects of substation design

Converter station design was carried out in the aim to substain the sardinianHV grid both in normal and emergency conditions.

SAPEI connection guarantee “black start” , starting in case of Sardinia blackout even thought with reduced performances, to participate at restarting of thegrid.

In case of pole fault, (converter station or cable), SAPEI can automaticallyswitch from bipolar to monopolar configuration , with ground or metallicswitch from bipolar to monopolar configuration , with ground or metallicreturn path , to guarantee at least 500 MW

Start/Stop sequences are provided to allow the maximum power range also inbipolar configuration (50 – 1000 MW).

The control system of SAPEI allows the full integration with existing SACOI linkin order to participate in frequency regulation of Sardinian HV grid

SAPEI – Operating mode

Operation in case of pole 1 converter fault

• Operation can be ensured at half nominal power (500 MW) without interruption of

the connection (current through pole 2 line and return through cable 1 after a

transient return through electrode in reverse direction)

Operation in case of pole 2 converter fault

• Operation can be ensured at half nominal power (500 MW) without

interruption of connection with current return through electrodes or

cable 2


Operation in case of cable 2 fault

• Operation can be ensured at half nominal power (500 MW) without

interruption of connection with current return through electrodes


Operation in case of cable 1 fault

• Operation can be assured at half nominal power (500 MW) after manual

reconfiguration of the circuits. Such reconfiguration requires a bipolar outservice that

can be planned after a temporary operation with electrodes in reverse mode.


SAPEI – Outline of the route

SAPEI - sea cable profile

Low-Medium depth L-M depthHigh depth

SAPEI - Cable design

Deep Water solution

Shallow Water solution

SAPEI – Land cables

Electrode cablecopper 1x1200 sqmm

Section of land cable trench Lazio side

1 Conduttore rotondo compatto a fili di rame, tamponato

2 Strato semiconduttivo interno

3 Isolante XLPE

4 Strato semiconduttivo esterno

5 Schermo a nastri di rame

6 Guaina di polietilene

7 Imbottitura in filato di polipropilene

8 Armatura a fili di acciaio zincato singolarmente isolati in politene

9 Fasciatura esterna in filato di polipropilene

500 kvdc pole cableCopper 1x1400 sqmm

1 Conduttore a conci di rame

2 Strato semiconduttivo

3Isolamento in strati di carta impregnato di miscela ad alta viscosità


5 Guaina in lega di piombo


7 Rinforzo a nastri di acciaio zincato

8 Guaina anticorrosiva di polietilene

SAPEI – Fiume Santo land cables route

1 Conduttore a conci di rame


3Isolamento in strati di carta impregnato di miscela ad alta viscosità


5 Guaina in lega di piombo


7 Rinforzo a nastri di acciaio zincato

500 kvdc pole cableCopper 1x1400 sqmm

8 Guaina anticorrosiva di polietilene

SAPEI –Principle risks for submarine cables and Environmental aspects

• Fishing activities

• Maritime traffic and relevant anchorage

• Presence of protected vegetation as Posidonia prateries along the

route

• Cetacean mammal sanctuary areas

This require definition of final route on basis of a detailed marine survey,

special protection for submarine cable and modalities of installation .

SAPEI – Survey

A detailed survey has been carried out along the authorized route

SAPEI – Marine cable protection (1)

The cable will be buried utilizing jetting

machine and7or trenching machine

driven by divers or through a ROV down

to -400 m depth

The burial depth will depend on the soil

characteristics: target 1m with minimum

acceptance 30 cm

In poseidonia fields, the cable will be laid on the

sea bed and fixed by special anchoring devices

SAPEI – marine cable protection (2)

When the bottom is rocky or irregular, thecable cannot be buried. According to thepracticability of the operation, the cablecould be protected by means of concretemattresses or rock dumping

sea bed and fixed by special anchoring devices

In the shore crossing portion the cable will be

protected by means of pre-installed pipes. The

pipes will be installed with the HDD tecinique

SAPEI – Pole 1 cable laying

SAPEI – Anode - Punta Tramontana

Upgraded anode 2500 ASACOI + SAPEI

Pre-existing SACOI anode 1500A

SAPEI – Converter stations

Fiume Santo

LatinaLatina

Latina converter station layout

Control room

filters

transformers Valve Hall

DC Hall

Control room

380kV national grid substation

380 kV AC Yard

sapei ± 500 kvdc - 1000 mw interconnection sardinia ... borgo sabotino sapei 24-01-14.pdf ·...

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